On Tue, 20 Feb 2024 07:29:25 +0000, <ankita@xxxxxxxxxx> wrote: > > From: Ankit Agrawal <ankita@xxxxxxxxxx> > > To provide VM with the ability to get device IO memory with NormalNC > property, map device MMIO in KVM for ARM64 at stage2 as NormalNC. > Having NormalNC S2 default puts guests in control (based on [1], > "Combining stage 1 and stage 2 memory type attributes") of device > MMIO regions memory mappings. The rules are summarized below: > ([(S1) - stage1], [(S2) - stage 2]) > > S1 | S2 | Result > NORMAL-WB | NORMAL-NC | NORMAL-NC > NORMAL-WT | NORMAL-NC | NORMAL-NC > NORMAL-NC | NORMAL-NC | NORMAL-NC > DEVICE<attr> | NORMAL-NC | DEVICE<attr> > > Still this cannot be generalized to non PCI devices such as GICv2. > There is insufficient information and uncertainity in the behavior > of non PCI driver. A driver must indicate support using the > new flag VM_ALLOW_ANY_UNCACHED. > > Adapt KVM to make use of the flag VM_ALLOW_ANY_UNCACHED as indicator to > activate the S2 setting to NormalNc. > > [1] section D8.5.5 of DDI0487J_a_a-profile_architecture_reference_manual.pdf > > Suggested-by: Catalin Marinas <catalin.marinas@xxxxxxx> > Acked-by: Jason Gunthorpe <jgg@xxxxxxxxxx> > Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx> > Signed-off-by: Ankit Agrawal <ankita@xxxxxxxxxx> Since people have asked for various commit message updates, I'll add my own: for the KVM/arm64 tree, the convention for the subject line is "KVM: arm64: Something starting with a capital". Thanks, M. -- Without deviation from the norm, progress is not possible.
